Substrate processing apparatus, substrate processing method, and storage medium

ABSTRACT

Disclosed is a substrate processing apparatus including: a substrate holding member that holds a peripheral portion of a substrate; a rotating member that includes a plate provided with the substrate holding member and rotates the substrate by rotating the plate; a fluid supply unit that is disposed at a center of the rotating member and supplies a processing liquid and an inert gas to a lower surface of the substrate held by the substrate holding member; and a controller that controls to perform a liquid processing by supplying the processing liquid to the lower surface of the substrate while rotating the substrate, and, after the liquid processing, to perform a drying processing of the substrate while supplying the inert gas to the lower surface of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2017-152612 filed on Aug. 7, 2017 with the Japan PatentOffice, the disclosure of which is incorporated herein in its entiretyby reference.

TECHNICAL FIELD

The present disclosure relates to a technique of drying a lower surfaceof a substrate after a liquid processing is performed on the substrateby supplying a processing liquid to the lower surface.

BACKGROUND

In a substrate processing apparatus used for manufacturing asemiconductor device, there is a case where a rinse processing isperformed on a lower surface of a substrate (e.g., a semiconductorwafer) by supplying a rinse liquid (e.g., deionized water) to the lowersurface while rotating the substrate about a vertical axis in ahorizontal posture. When performing the liquid processing, the substrateis held by a spin chuck (substrate rotating and holding mechanism)including a disk-shaped base member and a plurality of chuck membersprovided at a peripheral portion of the base member and configured tochuck a peripheral portion of the substrate. The “lower surface of thesubstrate” is a surface facing downward during the processing. Thesurface may be either a front surface that is a device forming surfaceor a rear surface that is a device non-forming surface.

After the rinse processing on the lower surface is completed, shake-offdrying is performed by rotating the substrate at a high speed. In orderto satisfactorily dry the substrate, a small circular drying area (drycore) may be first formed at a central portion of the substrate, and anouter peripheral edge of the drying area may be gradually expandedconcentrically. By doing so, even when particles are present in theliquid, the particles are driven away from the substrate together withthe liquid. Thus, it is possible to suppress particles from remaining onthe dried substrate.

When shake-off drying is performed, a gas having a low humidity anddesirably a low oxygen concentration (e.g., nitrogen gas) is supplied tothe lower surface of the substrate in order to promote drying andsuppress the occurrence of water marks (see, e.g., Japanese PatentLaid-Open Publication No. 2015-231030). Since the supply amount of thenitrogen gas influences the formation and expansion of the dry core, thesupply amount must be controlled within a suitable range. When thesupply amount of the nitrogen gas is excessive, the expanding speed ofthe dry core becomes excessive. Thus, a tear-off of the liquid film onthe outer side of the dry core (occurrence of liquid droplets separatedfrom the liquid film) may occur. When particles are present in a tornliquid droplet, the particles will be re-attached to the substrate afterdrying the liquid droplet.

Further, in parallel with the above-described liquid processing on thelower surface, a liquid processing, for example, a scrub cleaning or anatomize spray (AS) cleaning processing may be performed on an uppersurface of the substrate. In this case, particles derived fromsubstances removed from the substrate surface by the cleaning processingflow together with the processing liquid toward the peripheral portionof the substrate, and finally scatter to the outside of the substrate.The processing liquid including the particles may go around to the lowersurface and attached to the chuck members and the lower surface of thesubstrate around the chuck members.

SUMMARY

According to an embodiment of the present disclosure, there is provideda substrate processing apparatus including a substrate holding memberthat holds a peripheral portion of a substrate, a rotating member thatincludes a plate provided with the substrate holding member and rotatesthe substrate by rotating the plate, a fluid supply unit that isdisposed at a center of the rotating member and supplies a processingliquid and an inert gas to a lower surface of the substrate held by thesubstrate holding member, and a controller that controls to perform aliquid processing by supplying the processing liquid to the lowersurface of the substrate while rotating the substrate, and, after theliquid processing, to perform a drying processing of the substrate whilesupplying the inert gas to the lower surface of the substrate. Thecontroller controls to supply the inert gas at a first supply flow ratein a state where a liquid film is present at a central portion of thelower surface of the substrate after starting the drying processing, andsupply the inert gas at a second supply flow rate lower than the firstsupply flow rate after the liquid film is no longer present at thecentral portion of the lower surface.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view illustrating an overall configuration ofa substrate processing system according to an embodiment of a substrateprocessing apparatus of the present disclosure.

FIG. 2 is a schematic vertical sectional view of a processing unitincluded in a substrate liquid processing system of FIG. 1.

FIG. 3 is an enlarged cross-sectional view illustrating a vicinity of anejection port of a processing liquid and an ejection port of a dryinggas in the processing unit of FIG. 2.

FIG. 4 is a view for explaining progress of drying of a lower surface ofa wafer.

FIG. 5 is a view for explaining a defect that occurs during drying ofthe lower surface of the wafer.

FIG. 6 is a graph for explaining a transition of a supply amount ofnitrogen gas.

FIGS. 7A and 7B are views for explaining a modified substrate holdingmember. FIG. 7A is a side view illustrating the substrate holding memberafter modification, and FIG. 7B is a side view illustrating thesubstrate holding member before modification.

FIG. 8 is a perspective view of the modified substrate holding memberillustrated in FIG. 7A.

FIG. 9 is a view illustrating a positional relationship of the modifiedsubstrate holding member illustrated in FIG. 7A, a wafer held in thesubstrate holding member, and a brush.

FIGS. 10A to 10D are a schematic vertical sectional view illustrating anembodiment of a substrate holding and rotating mechanism provided with amovable partition plate.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawing, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

The present disclosure is to provide a technique capable of suppressingliquid droplets from being generated due to tear-off of a liquid film atthe outer side of a drying area when drying a lower surface of asubstrate, and suppressing particles from being attached to a lowersurface of a chuck member the lower surface of the substrate around thechuck member.

According to an embodiment of the present disclosure, there is provideda substrate processing apparatus including a substrate holding memberthat holds a peripheral portion of a substrate, a rotating member thatincludes a plate provided with the substrate holding member and rotatesthe substrate by rotating the plate, a fluid supply unit that isdisposed at a center of the rotating member and supplies a processingliquid and an inert gas to a lower surface of the substrate held by thesubstrate holding member, and a controller that controls to perform aliquid processing by supplying the processing liquid to the lowersurface of the substrate while rotating the substrate, and, after theliquid processing, to perform a drying processing of the substrate whilesupplying the inert gas to the lower surface of the substrate. Thecontroller controls to supply the inert gas at a first supply flow ratein a state where a liquid film is present at a central portion of thelower surface of the substrate after starting the drying processing, andsupply the inert gas at a second supply flow rate lower than the firstsupply flow rate after the liquid film is no longer present at thecentral portion of the lower surface.

In the above-described substrate processing apparatus, the first supplyflow rate in the drying processing is a flow rate sufficient to blow offthe processing liquid attached to the substrate holding member.

In the above-described substrate processing apparatus, in the liquidprocessing, the controller controls to supply the inert gas from thefluid supply unit at a third flow rate, and the second supply flow ratein the drying processing is lower than the third flow rate.

The above-described substrate processing apparatus further includes abrush that performs a scrub cleaning on an upper surface of thesubstrate held in the substrate holding member. The controller controlsto perform the scrub cleaning using the brush on the upper surface ofthe substrate while performing the liquid processing on the lowersurface of the substrate.

According to another embodiment of the present disclosure, there isprovided a substrate processing method for processing a substrate usinga substrate processing apparatus including a substrate holding memberthat holds a peripheral portion of a substrate, a rotating member thatincludes a plate provided with the substrate holding member and rotatesthe substrate by rotating the plate, and a fluid supply unit that isdisposed at the center of the rotating member and supplies a processingliquid and an inert gas to a lower surface of the substrate held by thesubstrate holding member. The substrate processing method includesperforming a liquid processing by supplying the processing liquid to thelower surface of the surface while rotating the substrate, and aftersupplying the processing liquid, performing a drying processing on thesubstrate while supplying the inert gas to the lower surface of thesubstrate. In the substrate processing method, the inert gas is suppliedat a first supply flow rate in a state where a liquid film is present ata central portion of the lower surface of the substrate after startingthe drying processing, and the inert gas is supplied at a second supplyflow rate lower than the first supply flow rate after the liquid film isno longer present at the central portion of the lower surface.

In the above-described substrate processing method, the first supplyflow rate in the drying processing is a flow rate sufficient to blow offthe processing liquid attached to the substrate holding member.

In the above-described substrate processing method, in the performing ofthe liquid processing, the inert gas is supplied from the fluid supplyunit at a third flow rate, and the second supply flow rate is lower thanthe third flow rate.

In the above-described substrate processing method, a scrub cleaning isperformed on the upper surface of the substrate using a brush when theliquid processing is performed on the lower surface of the substrate.

According to yet another embodiment of the present disclosure, there isprovided non-transitory computer-readable storage medium that stores aprogram that, when executed, causes a computer to execute theabove-described substrate processing method.

According to the embodiment of the present disclosure, the particlesattached to the substrate holding member may be blown away by supplyingthe inert gas at a relatively high flow rate while a relatively thickliquid film covers the entire lower surface of the substrate. Further,when the liquid film is no longer present at the center of the lowersurface of the substrate, the inert gas may be supplied at a relativelylow flow rate such that the speed at which the drying area expands issuppressed from becoming excessive. Therefore, it is possible tosuppress the occurrence of particles due to the tear-off of the liquid.

Hereinafter, various embodiments of the present disclosure will bedescribed with reference to the drawings.

FIG. 1 is a view illustrating a schematic configuration of a substrateprocessing system according to an embodiment of the present disclosure.Hereinafter, in order to clarify positional relationships, the X-axis,the Y-axis, and the Z-axis are defined as being orthogonal to eachother. The positive Z-axis direction is regarded as a vertically upwarddirection.

As illustrated in FIG. 1, a substrate processing system 1 includes acarry-in/out station 2 and a processing station 3. The carry-in/outstation 2 and the processing station 3 are provided adjacent to eachother.

The carry-in/out station 2 includes a carrier placing section 11 and atransfer section 12. A plurality of carriers C are placed in the carrierplacing section 11 to accommodate a plurality of wafers W horizontally.

The transfer section 12 is provided adjacent to the carrier placingsection 11, and includes a substrate transfer device 13 and a deliveryunit 14 therein. The substrate transfer device 13 includes a substrateholding mechanism configured to hold the wafer W. Further, the substratetransfer device 13 is movable horizontally and vertically, pivotablearound a vertical axis, and transfers the wafers W between the carriersC and the delivery unit 14 by using the substrate holding mechanism.

The processing station 3 is provided adjacent to the transfer section12. The processing station 3 includes a transfer section 15 and aplurality of processing units 16. The plurality of processing units 16are arranged side by side on both sides of the transfer section 15.

The transfer section 15 includes a substrate transfer device 17 therein.The substrate transfer device 17 includes a substrate holding mechanismconfigured to hold the wafer W. Further, the substrate transfer device17 is movable horizontally and vertically and pivotable around avertical axis. The substrate transfer device 17 transfers the wafers Wbetween the delivery unit 14 and the processing units 16 by using thesubstrate holding mechanism.

Each of the processing units 16 performs a predetermined substrateprocessing on the wafers W transferred by the substrate transfer device17.

Further, the substrate processing system 1 includes a control device 4.The control device 4 is, for example, a computer, and includes acontroller 18 and a storage unit 19. The storage unit 19 stores aprogram that controls various processings performed in the substrateprocessing system 1. The controller 18 controls the operations of thesubstrate processing system 1 by reading and executing the programstored in the storage unit 19.

Further, the program may be recorded in a computer-readable recordingmedium, and installed from the recording medium to the storage unit 19of the control device 4. The computer-readable recording medium may be,for example, a hard disc (HD), a flexible disc (FD), a compact disc(CD), a magnet optical disc (MO), or a memory card.

In the substrate processing system 1 configured as described above, thesubstrate transfer device 13 of the carry-in/out station 2 first takesout a wafer W from a carrier C placed in the carrier placing section 11,and then, places the taken wafer W on the delivery unit 14. The wafer Wplaced on the delivery unit 14 is taken out from the delivery unit 14 bythe substrate transfer device 17 of the processing station 3, andcarried into a processing unit 16.

The wafer W carried into the processing unit 16 is processed by theprocessing unit 16, and then, carried out from the processing unit 16and placed on the delivery unit 14 by the substrate transfer device 17.Then, the processed wafer W, which is placed on the delivery unit 14,returns to the carrier C of the carrier placing section 11 by thesubstrate transfer device 13.

Next, a schematic configuration of the processing unit 16 will bedescribed with reference to FIGS. 2 and 3. Unless otherwise specified,all members illustrates in FIG. 3 substantially correspond to a rotatingbody as a geometrical term.

As illustrated in FIG. 2, the processing unit 16 includes a chamber 20,a substrate holding and rotating mechanism 30 configured to hold androtate the wafer W, a liquid ejecting unit 40 that constitutes aprocessing liquid supply nozzle, and a recovery cup 50 configured torecover the processing liquid after being supplied to the wafer W.

The chamber 20 accommodates the substrate holding and rotating mechanism30, the liquid ejecting unit 40, and the recovery cup 50. A fan filterunit (FFU) 21 is provided on the ceiling of the chamber 20. The FFU 21forms a down flow within the chamber 20.

The substrate holding and rotating mechanism 30 is configured as amechanical chuck that holds the wafer W by a mechanical clamp mechanism.The substrate holding and rotating mechanism 30 includes a substrateholding unit 31, a rotation shaft 32, and a rotation motor (rotationdriving unit) 33. A rotation speed of the rotation motor 33 may becontinuously changed to an arbitrary value under the control of thecontrol device 4. The rotation motor 33 rotationally drives the rotationshaft 32, so that the wafer W held in a horizontal position by thesubstrate holding unit 31 rotates around the vertical axis.

The substrate holding unit 31 includes a disk-shaped base plate(plate-like body) 31 a and a plurality of holding members 31 b (chucks)provided on the peripheral portion of the base plate 31 a. The holdingmembers 31 b hold the periphery of the wafer W. In an embodiment, someof the plurality of holding members 31 b are movable support membersthat move back and forth with respect to the periphery of the wafer W toswitch between gripping and releasing of the wafer W, and the remainingholding members 31 b are immovable holding members (e.g., support pins).The rotation shaft 32 is formed of a hollow tubular body extending inthe vertical direction.

The rotation shaft 32 and the base plate 31 a are connected through aconnecting portion 34. The connecting portion 34 may be a separatecomponent from the rotation shaft 32 and the base plate 31 a, or may bean integral component with the rotation shaft 32 or the base plate 31 a.

The liquid ejecting unit 40 is formed as an elongated shaft-like memberextending in the vertical direction as a whole. The liquid ejecting unit40 includes a shaft portion 41 extending in the vertical direction and ahead portion 42. The shaft portion 41 is inserted into a cylindricalcavity 32 a inside the rotation shaft 32 of the substrate holding androtating mechanism 30. The shaft portion 41 and the rotation shaft 32are concentric to each other. A space serving as a gas passage 80 havingan annular cross-section is formed between the outer peripheral surfaceof the shaft portion 41 and the inner peripheral surface of the rotationshaft 32.

A drying gas is supplied from a drying gas supply mechanism 74 to thegas passage 80. The drying gas may have a low humidity so as to promotedrying, and may have a low oxygen concentration in order to suppressoccurrence of water marks. In the present embodiment, the drying gas maybe nitrogen gas that has a low humidity and also has a low oxygenconcentration. Although illustration and detailed description of theconfiguration of the drying gas supply mechanism 74 is omitted, thedrying gas supply mechanism 74 is constituted by, for example, a supplyline connected to a gas supply source, and an opening/closing valve anda flow rate control valve interposed in the supply line.

Inside the liquid ejecting unit 40, there is a cylindrical cavityextending in the vertical direction. A processing liquid supply pipe 43(only illustrated in FIG. 3) is provided inside the cavity. An upper endof the processing liquid supply pipe 43 is opened at the central portionof the upper surface of the head portion 42 of the liquid ejecting unit40 and serves as an liquid ejecting port 43 a that ejects the processingliquid toward the central portion of the lower surface of the wafer Wheld in the substrate holding and rotating mechanism 30 (see, e.g., theblack arrow in FIG. 3).

A rinse liquid, for example, deionized water (DIW) for cleaning thelower surface of the wafer W is supplied from a processing supplymechanism 72 (e.g., see FIG. 2) to the processing liquid supply pipe 43.Although illustration and detailed description of the configuration ofthe processing liquid supply mechanism 72 is omitted, the processingliquid supply mechanism 72 is constituted by, for example, a supply lineconnected to a gas supply source, and an opening/closing valve and aflow rate control valve interposed in the supply line. The processingliquid supply mechanism 72 may be configured to switch and supply therinse liquid and a processing liquid other than the rinse liquid, forexample, a chemical liquid (e.g., DHF).

At the central portion of the upper surface of the connecting portion34, a cylindrical recessed portion 34 b is formed to communicate withthe gas passage 80. Most of the lower side of the head portion 42 isaccommodated in the recessed portion 34 b. The head portion 42 includesa flange portion 42 a that protrudes radially outward beyond the outerperipheral end of the recessed portion 34 b. A gas flowing upward in thegas passage 80 flows through a space defined between an inner surface ofthe recessed portion 34 b and a surface of the head portion 42 oppositethereto, further flows through a gap between a lower surface of theflange portion 42 a and an upper surface 34 a of the connecting portion34, and is injected to a space between the lower surface of the wafer Wand the base plate 31 a in a substantially horizontal direction towardthe radially outer side (see, e.g., the white arrow in FIG. 3). That is,the gas injected from the outlet of the gap 82 is not directly sprayedto the lower surface of the wafer W. The outlet of the gap 82constitutes a gas injecting portion.

Further, even when the processing liquid supplied to the lower surfaceof the wafer W drops from the liquid ejecting port 43 a, it is possibleto suppress the processing liquid from entering the gas passage 80through the space 81 by the flange portion 42 a.

As illustrated in FIG. 2, the recovery cup 50 is disposed so as tosurround the substrate holding unit 31 of the substrate holding androtating mechanism 30, and captures the processing liquid scatteringfrom the rotating wafer W. The recovery cup 50 includes an immovablelower cup body 51 and an upper cup body 52 that is movable up and downbetween a raised position (the position illustrated in FIG. 2) and alowered position. The upper cup body 52 moves up and down by anelevating mechanism 53. When the upper cup body 53 is at the loweredposition, an upper end of the upper cup body 52 is positioned at aposition lower than the wafer W held by the substrate holding androtating mechanism 30. Therefore, when the upper cup body 52 is at thelowered position, it is possible to deliver the wafer W between thesubstrate holding mechanism (arm) of the substrate transfer device 17illustrated in FIG. 1 which has entered the chamber 20 and the substrateholding and rotating mechanism 30.

A discharge port 54 is formed at a bottom portion of the lower cup body51. The captured processing liquid and the atmosphere in the recoverycup 50 are discharged from the recovery cup through the discharge port54. A discharge pipe 55 is connected to the discharge port 54, and thedischarge pipe 55 is connected to a factory exhaust system (notillustrated) in a depressurized atmosphere.

The down flow of the clean air from the FFU 21 is drawn into therecovery cup 50 through an upper opening of the recovery cup 50 (theupper cup body 52), and is exhausted from the discharge port 54.Therefore, an air current indicated by an arrow F is generated in therecovery cup 50.

The processing unit 16 may include a processing liquid nozzle 61 thatsupplies a processing liquid to the upper surface of the wafer W held bythe substrate holding and rotating mechanism 30. The processing fluidnozzle 61 may be positioned at an arbitrary position between a positiondirectly above the center of the wafer W and a position directly abovethe periphery of the wafer W, and a standby position (home position)outside of the wafer W, by a nozzle arm (not illustrated). Theprocessing fluid nozzle 61 may supply a chemical liquid, a rinse liquid,or two fluids (to be described later in detail).

The processing unit 16 may include a brush 62 that performs a scrubcleaning on the upper surface of the wafer W held by the substrateholding and rotating mechanism 30. The brush 62 may be positioned at anarbitrary position between the central portion of the wafer W and theperipheral portion of the wafer W, and a standby position (homeposition) outside of the wafer W, by the nozzle arm (not illustrated).

Next, an example of processing performed by the processing unit 16 willbe described with reference to FIG. 6. Here, it is assumed that adeionized water rinse processing is performed on the lower surface (inthe embodiment, a front surface on which a pattern is formed) whileperforming a scrub cleaning on the upper surface of the wafer W (in theembodiment, a rear surface on which a pattern is not formed). Thisprocessing is performed for the purpose of, for example, sufficientlyremoving particles from the rear surface of the wafer W to suppressdefocusing during exposure of the wafer W. In this processing, onlydeionized water DIW is used as a processing liquid, and no chemicalliquid is used. Further, in FIG. 1, one of the 12 processing units 16 issubstituted with a reverser (not illustrated) that reverses the wafer.

Before being carried into the processing unit 16, the substrate transferdevice 17 holding wafer W that is reversed by the reverser (notillustrated) so that the rear surface becomes an upper surface entersthe chamber 20, and the wafer W is transferred to the substrate holdingunit 31 of the substrate holding and rotating mechanism 30. Thereafter,the substrate holding mechanism (arm) is retracted from the chamber 20,and the upper cup body 52 is raised to the raised position.

Next, the substrate holding and rotating mechanism 30 rotates the waferW. The wafer W continues to rotate until a series of processing on thewafer W is completed. In this state, while supplying deionized water tothe upper surface of the wafer W, the rotating brush 62 is brought intocontact with the central portion of the wafer and the brush 62 is movedto the peripheral portion of the wafer W, so that the scrub cleaningprocessing is performed on the entire upper surface of the wafer W (timeT0 to T1 in FIG. 6).

The brush 62 is held by an arm (not illustrated) incorporating a brushrotating mechanism, and is movable between the central portion and theperipheral portion of the wafer W. The supply of deionized water to theupper surface of the wafer W may be performed by a deionized waterejecting unit incorporated in or integrated with the brush 62, or by theprocessing fluid nozzle 61 separately provided from the brush 62.

After completion of the scrub cleaning processing, the brush 62 movesaway from the upper surface of the wafer W, and moves to the standbyposition outside the wafer W. Deionized water is supplied from theprocessing fluid nozzle 61 to the central portion of the upper surfaceof the wafer W, and the rinse processing is performed on the uppersurface of the wafer W (time T1 to T2 in FIG. 6). After completion ofthe rinse processing, the supply of deionized water to the upper surfaceof the wafer W is stopped, and the shake-off drying of the wafer W isperformed (time T2 to T4 in FIG. 6).

While performing the scrub cleaning processing and the rinse processingon the upper surface of the wafer W described above, a rinse processingof the wafer W is performed in order to suppress contamination of thelower surface (device forming surface) of the wafer W (time T0 to T2 inFIG. 6).

The rinse processing is performed by supplying deionized water as arinse liquid to the central portion of the lower surface of the rotatingwafer W from the liquid ejecting port 43 a of the liquid ejecting unit40. The deionized water supplied to the central portion of the lowersurface of the wafer W spreads and flows radially outward due tocentrifugal force, and scatters outward from the periphery of the waferW. At this time, the entire lower surface of the wafer W is covered withthe liquid film of the deionized water. The liquid film of the deionizedwater blocks deionized water including particles that are going aroundfrom the upper surface to the lower surface of the wafer W.

In order to suppress the rinse liquid from going around from the uppersurface to the lower surface of the wafer, or from the lower surface tothe upper surface, the rinse processing on the upper surface of thewafer and the rinse processing on the wafer may be completed at the sametime or substantially at the same time. That is, the supply of the rinseliquid to the upper surface of the wafer W and the supply of the rinseliquid to the lower surface of the wafer W may be stopped substantiallyat the same time (time T2 in FIG. 6).

The liquid processing step has been described. Next, a drying step, thatis, an operation of shifting to the time T2 in FIG. 6 will be described.The drying step is started when supply of the rinse liquid is stopped.

In the drying step, the oxygen concentration in the space between thewafer W and the base plate 31 a of the substrate holding unit 31 may belowered such that water marks (which may cause particles) does not occuron the lower surface of the wafer W. Therefore, nitrogen gas is injectedinto the space from the outlet of the gap 82 between the lower surfaceof the flange portion 42 a of the head portion 42 and the upper surface34 a of the connecting portion 34.

In the example of FIG. 6, nitrogen gas is injected from the outlet (thegas injecting portion) of the gap 82 at a flow rate FR1 (e.g., 20 L/min)before the time T2, but the present disclosure is not limited thereto.The nitrogen gas may not be injected before the time T2.

As soon as the supply of the rinse liquid (deionized water) to the lowersurface of the wafer W is stopped (that is, immediately at the time T2),nitrogen gas is injected at a high flow rate FR2 (e.g., 60 L/min). Thetiming of starting the injection of the nitrogen gas does not need to becompletely simultaneously with the stop of the supply of the rinseliquid, and may be slightly before or after the stop of the supply ofthe rinse liquid.

The nitrogen gas injected at a high flow rate flows substantiallyuniformly with respect to the circumferential direction of the wafer Wto the peripheral portion of the wafer W, and blows away the deionizedwater containing particles attached to the holding member 31 b. Theparticles contained in the deionized water are mainly derived fromsubstances removed from the upper surface of the wafer W by the scrubcleaning.

At the time T2 and a time slightly after the time T2 (e.g., time T3 inFIG. 6), since a liquid film having a sufficient thickness is present onthe lower surface of the wafer W, even if nitrogen gas is injected at ahigh flow rate from the outlet (gas injecting portion) of the gap 82,the liquid film on the lower surface of the wafer W is not destroyed bythe influence of the injected gas.

When the supply of the rinse liquid to the lower surface of the wafer Wis stopped, and after a while, since the deionized water present on thelower surface of the wafer W flows to the periphery of the wafer W bycentrifugal force, first initially, in the central portion of the waferW, a liquid film LF of the deionized water is disappeared and the frontsurface (lower surface) of the wafer W is exposed. That is, a smallcircular drying area DA (also referred to as a “dry core”) is formed inthe central portion of the wafer W (also see, e.g., FIG. 4).

Thereafter, the drying area DA expands by lapse of time, and finally theentire lower surface of the wafer W is dried. During drying, a boundaryB between the liquid film LF and the drying area DA may smoothly moveradially outward while maintaining a substantially circular shape.

When the moving speed of the boundary B is inappropriate, there is apossibility that the liquid film is torn out and liquid droplets LD areseparated from the liquid film. The situation when this phenomenonoccurs is schematically illustrated in FIG. 6. The tear-off of theliquid droplets tends to occur in a case where the surface of the waferis hydrophobic and a case where both a hydrophobic area and ahydrophilic area coexist on the surface of the wafer, and especially itis likely to occur in the latter case. As a specific example, under thecircumstance where a plurality of rectangular circuit patterns areformed on the surface of the wafer W in a matrix form, there is a casewhere many hydrophobic portions are present on the surface of therectangular patterns, and the area between the rectangles ishydrophilic. In this case, an event occurs, in which liquid dropletsremain on the circuit patterns, and thereafter the liquid droplets aredried.

Particles may be present in the liquid film of the rinse liquid(deionized water). The particles may have originally been attached tothe wafer W or may have been taken into the liquid film after beingwound up by the nitrogen gas injected from the outlet of the gap 82.When the liquid droplets containing the particles are dried, theparticles are attached to the surface of the wafer W. When the liquiddroplets containing particles remain in the circuit pattern portion andthe liquid droplets are dried, yield is adversely affected.

Meanwhile, even though particles are present in the liquid film, asdescribed above, when the boundary B between the liquid film LF and thedrying area DA maintains a substantially circular shape and smoothlymoves radially outward, such a problem does not occur. That is, in thiscase, the particles in the liquid film move radially outward togetherwith the liquid film and are discharged to the outside of the wafer Wtogether with the liquid film, so that the particles do not remain onthe surface of the wafer W.

Nitrogen gas is a low humidity gas (the same applies to an inert gassuch as Ar gas). Thus, when the nitrogen gas flows through the spacebetween the lower surface of the wafer W and the base plate 31 a (thespace below the wafer), the space below the wafer is maintained at a lowhumidity, and the drying of the lower surface of the wafer W ispromoted. Therefore, when the nitrogen gas is continuously injected at ahigh flow rate from the outlet (gas injecting portion) of the gap 82,the situation as illustrated in FIG. 5 may occur.

In the present embodiment, at the time T3 after the time T2, the flowrate of the nitrogen gas injected from the outlet of the gap 82 isdecreased to FR3 (e.g., 10 L/min). Therefore, the drying of the lowersurface of the wafer is suppressed, so that the drying proceeds in asuitable form as illustrated in FIG. 4.

The time T3 at which the flow rate of the nitrogen gas is decreased maybe set to a time when the liquid film is not present at the centralportion of the lower surface of the wafer W, that is, a time when thedry core DA is formed at the central portion of the lower surface of thewafer W. The time T3 depends on, for example, the flow rate of the highflow rate FR2 or a contact angle of the substrate, and is a numericalvalue obtained by experiments. Since the event illustrated in FIG. 5occurs after the boundary B moves radially outward to some extent, thetime T3 may be a time slightly after the dry core is formed at thecentral portion of the lower surface of the wafer W. Further, the timeT3 may be a time slightly before the dry core is formed at the center ofthe lower surface of the wafer W.

The rotation speed of the wafer W may be constant in the entire dryingprocessing. However, the tear-off of the liquid film LF is likely tooccur when the boundary B is at a position close to a periphery WE ofthe wafer W. The reason is that, as the boundary B approaches theperiphery WE, the liquid film LF becomes thinner, and a force ofexpanding the liquid film LF increases. When the boundary B approachesthe periphery WE, the force of expanding the liquid film LF may besuppressed by reducing the rotation speed of the wafer W to a low level.

Drying of the upper surface of the wafer W will not be described indetail in this specification. For example, by using a known method ofsupplying a drying gas such as nitrogen gas is supplied from a dryinggas nozzle (not illustrated) to the rotating wafer W while supplying therinse liquid from the processing fluid nozzle 61 to the rotating waferW, and moving both a radial direction position where the nitrogen gascollides with the wafer W (referred to as a “radial direction positionPN”) and a radial direction position where the rinse liquid collideswith the wafer W (referred to as a “radial direction position PR”)radially outside while maintaining the radial direction position PNradially inside the radial direction position PR, the drying may besatisfactorily performed while controlling the moving speed of theboundary between the drying area and the liquid film. That is, withrespect to the upper surface of the wafer W, the tear-off of the liquidfilm may be suppressed by a known method, thereby performing drying inwhich particles do not remain.

According to the embodiment, when the nitrogen gas is supplied at arelatively high flow rate to the space below the wafer at the beginningof the drying step, the particles attached to the holding member 31B(and the surface of wafer W around the holding member) may be removedwithout adversely affecting the drying of the lower surface of the waferW. Thereafter, when the nitrogen gas is supplied at a relatively lowflow rate, the boundary between the liquid film LF and drying area DAmay be smoothly moved radially outward while maintaining the boundarysubstantially circular shape.

In the above-described embodiment, the cleaning processing is performedin a state where the rear surface of the wafer W (the device non-formingsurface) faces upward and the front surface of the wafer W (deviceforming surface) faces downward, but the present disclosure is notlimited thereto. The cleaning processing may be performed in a statewhere the front surface of the wafer W faces upward and the rear surfaceof the wafer W faces downward. Further, the cleaning processing may beperformed only on the surface of the wafer W facing downward withoutperforming the cleaning processing on the surface of the wafer W facingupward.

A two-fluid cleaning processing may be performed instead of performingthe scrub cleaning processing on the upper surface of the wafer W. Thetwo-fluid cleaning is cleaning performed by spraying, onto the wafer W,two fluids, which are formed of a mixed fluid of a gas and droplets of aprocessing liquid (here, deionized water) made into mist by a gas (e.g.,nitrogen gas), in the processing fluid nozzle 61 configured as atwo-fluid nozzle. At this time, the processing fluid nozzle 61reciprocates between the central portion and the peripheral portion ofthe wafer W by a nozzle arm (not illustrated) while injecting the twofluids. Therefore, the particles attached to the upper surface of thewafer W are removed by the energy of the two fluids. In this case, thesupply of the nitrogen gas is stopped while continuing the supply of thedeionized water to the processing fluid nozzle 61, and the deionizedwater that is not made into mist is supplied from the processing fluidnozzle 61 to the central portion of the upper surface of the wafer,thereby performing the rinse processing on the upper surface of thewafer W.

The substrate serving as a processing target is not limited to thesemiconductor wafer (wafer W), but may be another kind of substrate suchas, for example, a glass substrate or a ceramic substrate as long as thesubstrate is a disk-shaped substrate to be processed in a rotatingstate.

Next, referring to FIGS. 7A, 7B, 8, and 9, descriptions will be made ona holding member that may be suitably used for scrub cleaning. Theholding member 31 b schematically illustrated in FIG. 2 has a shape, forexample, illustrated in FIGS. 7A, 7B, 8, and 9. That is, the holdingmember 31 b has a holding portion (wafer holding claw) 311 which is incontact with the periphery of the wafer W on one side, and a pressedportion 312 on the other side. The holding portion 311 is pivotallyattached to the base plate 31 a (not illustrated in FIGS. 7A, 7B, 8, and9) by a pin (not illustrated) inserted in a hole 313. When the pressedportion 312 is pushed up from below by a pressing member (notillustrated), the holding portion 311 is pivoted and moved to a releasedposition away from the wafer W. Due to gravity acting on the heavypressed portion 312 by the pressing member, the holding portion 311 ispivoted and moved to a holding position where the periphery of the waferW is held. For details of the above mechanism, refer to Japanese PatentLaid-Open Publication No. 10-209254 (this is a publication related tothe prior application by the present applicant), particularly, FIGS. 5and 8 thereof.

The holding member illustrated in FIGS. 7A, 7B, 8, and 9 is a holdingmember that is modified from a part of a holding member illustrated inFIGS. 5 and 8 of Japanese Patent Laid-Open Publication No. 10-209254.FIG. 7B illustrates a prior art, and FIG. 7A illustrates an embodimentof the present disclosure. In FIG. 7A, the height of the holding portion(wafer holding claw) 311 is low. Two broken lines extending across FIGS.7A and 7B indicate the thickness of the wafer W.

By lowering the height of holding portion 311 in this manner, asillustrated in FIG. 9, the brush 62 may be brought into contact with theradially outermost portion (that is, the entire region radially inwardof a bevel portion) of the flat portion of the upper surface of thewafer W. That is, it is possible to reliably remove the particles fromthe entire flat portion of the upper surface of the wafer W.

Further, by lowering the height of holding portion 311, it is possibleto reduce liquid splashing caused by the processing liquid flowing fromthe central portion of the wafer W toward the peripheral portion in theholding portion 311.

Further, as illustrated in FIG. 8, the holding portion 311 includes afirst portion 311 a and a second portion 311 b, and a gap 311 c isformed between the first portion 311 a and the second portion 311 b. Inaddition, the first portion 311 a and the second portion 311 b arethinned toward the radially outer side of the wafer W. By doing so, theprocessing liquid easily passes through the holding portion 311, so thatthe liquid splashing may be further reduced.

Further, as illustrated in FIG. 7A, an upper surface 311 d of theholding portion 311 is inclined so as to be lowered toward the radiallyouter side of the wafer W (when in the holding position). Therefore, theprocessing liquid easily climbs over the holding portion 311, so thatthe liquid splashing may be further reduced.

Next, another embodiment of a mechanism that supplies nitrogen gas to asubstrate holding portion and a region below the wafer will be describedwith reference to FIGS. 10A to 10D. In FIGS. 10A to 10D, the samemembers as the members illustrated in FIG. 2 are denoted by the samereference numerals.

In the embodiment of FIGS. 10A to 10D, a plurality of, for example,three support columns 104 are provided on the base plate 31 a of thesubstrate holding portion. A partition plate 105 is attached to thesupport column 104 to partition a space between the lower surface of thewafer W and the upper surface of the base plate 31 a. Depending on thepressure difference between the space above the partition plate 105 andthe space below the partition plate 105, the partition plate 105 maysmoothly move up and down between a lower limit position (the positionillustrated in FIGS. 10A to 10C) and a upper limit position (theposition illustrated in FIG. 10D), along the support column 104. A wafersupport member 106 is provided on an upper portion of each column 104.

Two tubular bodies 107 and 108 are arranged inside the hollow rotatingshaft 32 coaxially with the rotating shaft 32. The inside of the hollowtubular bodies is configured as a rinse liquid passage, and an outlet ofthe upper end of the rinse liquid passage is a rinse liquid ejectingport 101. The rinse liquid is ejected from the rinse liquid ejectingport 101 directly upward.

A first gas passage is formed between the tubular body 107 and thetubular body 108, and an outlet of the upper end of the first gaspassage is configured as a first gas ejecting port 102. An inert gas,for example nitrogen gas is supplied outward in radial direction(outside of the wafer W in the radial direction) from the first gasejecting port 102.

A second gas passage is formed between the rotating shaft 32 and thetubular body 107, and an outlet of the upper end of the second gaspassage is configured as a second gas ejecting port 103. An inert gas,for example nitrogen gas is supplied outward in radial direction fromthe second gas ejecting port 103.

Next, descriptions will be made on a procedure of performing a scrubcleaning processing on the upper surface of the wafer W and a rinseprocessing on the lower surface of the wafer W using the substrateprocessing apparatus of FIGS. 10A to 10D. While performing a series ofthe following processing steps, the wafer W is rotating through theprocessing steps.

FIG. 10A illustrates a cleaning step. In the cleaning step, a rinseprocessing is performed by supplying the rinse liquid (deionized water)from the rinse liquid ejecting port 101 to the central portion of thelower surface of the wafer W, while supplying deionized water to theupper surface of the wafer W and performing the scrub cleaning by thebrush 62. The lower surface of the wafer W is covered with the liquidfilm of the rinse liquid. At this time, nitrogen gas is supplied fromthe first gas ejecting port 102, whereas nitrogen gas is not suppliedfrom the second gas ejecting port 103. Therefore, since the pressure ofthe space above the partition plate 105 increases, the partition plate105 is positioned at the lower limit position.

FIG. 10B illustrates a rinsing step performed following the cleaningstep. In the rinsing step, a rinse processing is performed by supplyingthe rinse liquid (deionized water) from the rinse liquid ejecting port101 to the central portion of the lower surface of the wafer W, and atthe same time, a rinse processing is performed by supplying the rinseliquid (deionized water) to the upper surface of the wafer W. The lowersurface of the wafer W is covered with the liquid film of the rinseliquid. Also at this time, the nitrogen gas is supplied from the firstgas ejecting port 102, whereas the nitrogen gas is not supplied from thesecond gas ejecting port 103. Therefore, since the pressure of the spaceabove the partition plate 105 increases, the partition plate 105 ispositioned at the lower limit position.

FIGS. 10C and 10D illustrate a drying step performed following therinsing step. When transitioning from the rinsing step to the dryingstep, the supply of rinse liquid to the upper surface and lower surfaceof the wafer W is stopped.

FIG. 10C illustrates a state of an initial stage of the drying step.Also at this time, the nitrogen gas is supplied from the first gasejecting port 102, whereas the nitrogen gas is not supplied from thesecond gas ejecting port 103. Therefore, since the pressure of the spaceabove the partition plate 105 increases, the partition plate 105 ispositioned at the lower limit position.

FIG. 10D illustrates a state of a later stage of the drying step. Thelater stage of the drying step is timing after the rinse liquid isremoved from at least a part of the lower surface of the wafer W and thepart of the lower surface is started to be exposed. At this time, thesupply of the nitrogen gas from the first gas ejecting port 102 isstopped, and the supply of the nitrogen gas from the second gas ejectingport 103 is performed. Therefore, since the pressure of the space belowthe partition plate 105 increases, the partition plate 105 is positionedat the upper limit position. As a result, the lower surface of the waferW is covered with the partition plate 105 which is close to the lowersurface. Therefore, it is possible to suppress contaminated mistdrifting in the space below the wafer W from adhering to the lowersurface of the wafer W.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A substrate processing method for processing asubstrate comprising: providing a substrate processing apparatusincluding a substrate holder configured to hold a peripheral portion ofa substrate a rotator that includes a plate provided with the substrateholder configured to rotate the substrate by rotating the plate and afluid supply that is disposed at a center of the rotator and configuredto supply a processing liquid and an inert gas to a lower surface of thesubstrate held by the substrate holder first supplying the processingliquid to the lower surface of the substrate while rotating thesubstrate, thereby performing a liquid processing on the substrate;after the first supplying performing a dry processing on the substrateby second supplying the inert gas upwardly to the lower surface of thesubstrate at a first supply flow rate in a state where a liquid filmcovers the lower surface of the substrate including a central portionthereof; and after the second supplying, third supplying the inert gasupwardly to the lower surface of the substrate at a second supply flowrate lower than the first supply flow rate, wherein the inert gas issupplied at the second supply flow rate in the third supplying when adry core, surrounded by the liquid film covering the lower surface ofthe substrate, is formed at the central portion of the lower surface ofthe substrate, thereby completing the dry processing on the substratethe substrate.
 2. The substrate processing method of claim 1, wherein,in the first supplying, a portion of the processing liquid is attachedto the substrate holder and the first supply flow rate is a flow ratesufficient to blow off the processing liquid attached to the substrateholder.
 3. The substrate processing method of claim 1, wherein, in thefirst supplying, the inert gas is supplied from the fluid supply at athird supply flow rate, and the second supply flow rate is lower thanthe third supply flow rate.
 4. The substrate processing method of claim1, further comprising scrub cleaning an upper surface of the substrateusing a brush when the first supplying is performed on the lower surfaceof the substrate.
 5. A non-transitory computer-readable storage mediumthat stores a program that, when executed, causes a computer to executethe substrate processing method of claim
 1. 6. The substrate processingmethod of claim 2, wherein, in the first supplying, the inert gas issupplied from the fluid supply at a third supply flow rate, and thesecond supply flow rate is lower than the third supply flow rate.
 7. Thesubstrate processing method of claim 2, further comprising scrubcleaning an upper surface of the substrate using a brush when the firstsupplying is performed on the lower surface of the substrate.
 8. Thesubstrate processing method of claim 3, further comprising scrubcleaning an upper surface of the substrate using a brush when the firstsupplying is performed on the lower surface of the substrate.
 9. Thesubstrate processing method of claim 6, a further comprising scrubcleaning an upper surface of the substrate using a brush when the firstsupplying is performed on the lower surface of the substrate.